Crank assembly



June 19, 1945.

J. S; SHARPE CRANK ASSEMBLY 4 Sheets-Shet 1 Filed Jan; 16, 1941 June 19, 1945. J. s. SHARPE CRANK AS SEMBLY Filed Jan. 16 1941 4 Sheets-Sheet 2 June 19, 1945'.

Q J. 5. SHARPE CRANK ASSEMBLY Filed Jan. 16, 1941 4 sheets-sheet 4 Patented June 19, 1945 UNITED STATES PATENT OFFICE I I 2,378,507 I CRANK ASSEMBLY "John S. Sharpe, Haverford, Pa. A plication Jammie, 1941, Serial No. 1374, 763

' 3Claims remap-580) A principal object of this invention is to-provide an improved form of-crank assembly 'for Combustion engines, said assembly incorporating I adjustable means for varying the compression ratio of the engine cylinder or cylinders.

- Another object of the invention is to provide animproved true stroke crank assembly primarily for combustion engines of the radial type, said assembly eliminating thenecessity for. the conventional master rod and affording-asubstantially uniform distributionof thrusts imposed upon the crank shaft from the pistons.

' Still another object of the inventionis to provide an improved crank assembly for combustion engines of the radial type which-shall combine the desirable true strokecharacteristics with means for varying the compression ratioof the respective cylinders. I I I I A still further'object of the invention is to provide a variable compression crank assembly having improved means for regulatingthe timing of the ignition and of the valves in accordance with the variations in compression ratio. I

The invention further resides in the novel structural details and arrangements hereinafter described and illustrated in the attached drawings,

wherein V I a a Figure 1 is a vertical sectional view showing'a crank'assembly of a combustion engineofrthe radial type made in tion; Fig. 2 is a section on the line 2-2,' Fig. -1';

Figs. 3, 4, 5 and 6 are diagrammatic views illustrating certain characteristics of the mechanism shown in Figs. '1 and 2; I

Fig. 7 is a diagrammatic view showing a radial engine comprising a crank assembly made in accordance with theinvention; Fig. 8 is a view illustrating the mechanioal detailsof theengine assembly, including the various control elements unit; and

fig; 9 is a view correspondingv to Fig. .1 and illustrtaing a modification invention.- I

' With reference particularly to Figs. 1 and '2, l -is the crank case of aradial engine and 2 the cylinders. Journaled in the crank case upon bearings-'3 and 4 is a crank shaft '5, the crank 6 of which is counterbalanced by weights 1, "l. Journaled on thecrank pin is a connecting rod withinthe scope of the member 8 to which are pivotallysecureithrough v the medium of wrist pins 9; the connecting rods H of 'the severalpistons which-operate in the usual manner Within'the cylinders In Figs.

accordance with myinvenassociated with the crank axis of *the shaft 5.

3 and 5, thepistons are designated by the reference numeral-l2. Thus the pistons are operatively connected to the crank shaft through the intermediate member 8, which, as previousl set forth, is journaled on the crank 6.

The member 8 comprisesan internal gear l3 concentric with the axis "of the crank pin B. The gear 13 meshes with a gear l'd-whichis journaled on bearings I don the arm'fia of the crank. The gear 44 meshes also with an internal gear l8 which is of the same pitch diameter-as the-gear l3 and is supported in the casing l, as hereinafter described, concentrically withthe 30th of the internal gears 13 and l fi arebeveled', and the gear M, which may bein the form of a simple spur, is correspondinglyinclinedto the axis of' the shaft 5.

The teethofthe gears |3-and l6'are formed by 1 geared connection between the member 8 and the casing is to maintain themember 8 substantially fixed with respect to its own axis on the crank 6 while permitting the member .8 to move bodily in the annularpath described by the crank. Thus thetorque thrusts from the several pistons are transmitted through the connecting rods II and the member 8 to the crank B with substantial uniformity, the entire assembly being accurately balanced with respect to said thrusts and being free from the unbalanced forces and resulting vibrations which are'inherent in the conventional assembly employing a master rod.

The gear lfi -is supported in the casing l-in a 'mannerto permit of the angular adjustment of this gear about its own axis, which as previously set-forth corresponds to the axis of theshaft 5. In the present instance, the gear is provided with a peripheral flange I I! which is-fittedaccurately into a recessed seat in the inner wall of the casing,

as best illustrated in Fig. 1, and a ring l8 secured '2'! andi28 on the casing I, see Fig. 2. One end of the-shaft carriesa bevel pinion 29 which meshes with apinion 30* carried by a shaft 3I suitably journaled in the casing, and the shaft 3| is connected to asuitable manual or other actuator,

as hereinafter described. It will be apparent that actuation of the worm 25 will effect an angular adjustment about its axis of the gear I6, and through the intermediate gear l4 of the gear I3 and of the member 8 of which this latter gear forms a part. Angular adjustment of the member 8 with respect to its axis in the crank 6 Will effect an adjustment of the pistons [2 in their respective cylinders, and this adjustment of the pistons will be uniform.

The adjustment of the parts as described is best illustrated in Figs. 3 to 6, inclusive. If it be assumed that originally the parts are as shown in Fig. 3, wherein at the top of the piston stroke the connecting rod H is in line with the longitudinal axis of the cylinder, and wherein further the axes of the shaft 5 and of the crank 6 occupy a common plane which includes the lon. gitudinal center line of the cylinder, then each of the wrist pins 9 which connect the respective connecting rods to the member 8 will, as the crank shaft rotates, move in a circle the center of which is also intersected by said plane. This is the condition of maximum compression within the respective cylinders.

With reference to Figs. 3 and 4, 0. represents the axis of the shaft 5 and b the axis of the crank 6. Under the circumstances described, the center of the wrist pin 9 will describe a circular path indicated at c. In Fig. 4, the relative position of the gears I3, 14 and I6, corresponding to the position of the gears shown in Fig. 3 and described above, is illustrated. Let us assume now that the gear I6 is adjusted through the medium of the worm 25 as previously described through an angle shown in Fig. 6. In this movementof the gear IS, the point d, Fig. 4, will move to the position in which it is shown in Fig. 6. Similarly the gear. l3 will be adjusted in the same direction through a corresponding angle :12 so that the point e in Fig. 4 will move to the position shown in Fig. 6. As a result of this movement of the gears, the member 8 will be adjusted about the axis b of the crank 6 through an angle, see Fig. 5, corresponding to the angular movement of the gear l3, as indicated by the same reference character in Fig. 6. As a result of this angular movement of the member 8, the piston 12 will be retracted in its cylinder to the extent illustrated in Fig. 5, and also as aresult ofthe aforedescribed adjustment, the wrist pin 9 will, as the crank shaft rotates, describe a. path indicated in Fig. by the circle 0'. In this movement of the wrist pin 9, the piston will reach the top of its stroke when the piston rod H extends radially to the circle 0, as indicated by z the line g in Fig. 5. It will be apparent that by reason of the aforedescribed adjustment, the piston l2 at the top of its stroke will approach less closely to the cylinder head than in the original adjustment of the parts illustrated in Fig. 3, and that, therefore, the compression ratio in the cylinder will be materially reduced. It will be understood that adjustment of the member 8 as described affects the compression in each of the cylinders of the engine to exactly the same extent.

It will be noted by reference to Figs. 3 and 5 that the adjustment of the parts as previously set forth results also in a change in the relation between the movement of the crank shaft and the stroke of the piston. Thus when the parts are as illustrated in Figs. 3 and 4, the piston 12 reaches the top of its stroke at the moment when the crank 6, as indicated by the letter b, lies in closest proximity to or on the longitudinal axis 39 and 4|.

of the engine cylinder. After the adjustment illustrated in Figs. 5 and 6, however, it will be noted that when the axis of the crank b occupies this same relative position, the piston l2 has not reached the top of its stroke, since the connecting rod ll lies slightly out of alignment with the radial line g extending from the center of the cincle c. The wrist pin 9 must, therefore, move through the small angle between the point It and the line g before the piston l2 reaches the top of its stroke. Assuming, therefore, that the ignition is timed so as to create the spark in the cylinder at the time that the parts occupy the relative positions illustrated in Fig. 3, at which time the piston is at the top of its stroke, then this timing, if maintained, would result, after adjust ment of the parts as illustrated in Figs. 5 and 6, in the creation of the spark slightly in advance of the top of the piston stroke. If it be desired to maintain the original relative timing, therefore, adjustment must be made, through the distributor for example, for delaying or retarding the spark until after the axis b of the crank 6 shall have moved slightly beyond the positions in which it is shown in Figs. 3 and 5.

In Figs. 2 and 8, I have illustrated diagrammatically a. means for adjusting the timing of the ignition in accordance with adjustments in the compression ratio as .described above and in direct relation to the extent of such adjustment so that the timing of the ignition may remain relatively the same under all conditions of compression adjustment. It will be noted by reference to Fig. 2 that the shaft 26, which carries the worm 25 as previously described, carries also at one end a Worm 32 which meshes with a segmental worm wheel 33 on a shaft 34 suitably journaled in the casing. Referring now to Fig. 8, it will be noted that the shaft 34 carries a cam 35 which is operatively connected through a bell crank lever 36 with the adjustable head 31 of the distributor 38, this distributor being operatively connected in the conventional manner with the crank shaft 5 through the medium of bevel gears With this arrangement, any adjustment of the elements of the crank assembly, through the medium of the worm 25 as previously described, will result in an adjustment of the distributor 38, and the cam 35 may be so formed that the adjustment of the distributor to retard or advance the ignition spark will be such as to correct or to compensate for the maladjustment between the crank movement and the piston stroke resulting from the aforedescribed compressionadjustment.

A similar compensating adjustment of the timing of the valves may be effected through the shaft 34, as illustrated in Fig. 8. In this case, the valve-actuating cam 42 is journaled freely on the crank shaft 5, and is rotated in timed rela tion with the rotation of the crank shaft through gears 43 and 44 and a pinion 45 directly connected with the gear 44 and meshing with an internal gear 46 in the cam ring 42. 4'! and 48 constitute the rods which operatively connect the valves (not shown) with the cam 42. The shaft 49, which carries the gears 44 and 45, is in this instance mounted upon an arm 5| which is pivotally supported at its inner end upon the crank shaft 5 and which has at its outer end a rack 52 which meshes with a suitable gear element 53 on the shaft 34. With this arrangement, any adjustment of the shaft 34 will cause a swinging of the arm 5| about the axis of the shaft 5 and a corresponding adjustment of the gears 44 and 45 Preferably, these stops 54 and 55, as illustrated, I

are adjustable, so that the actual extent of the maximum adjustment of the gear wheel l6 may be regulated as required.

The shaft 3|, which carries the bevel pinion 30, may as previously set forth be connected to any desired form of actuator, and in Fig. 7, I have illustrated this shaft as connected through a rod 56 and universal joints 5! and 58 with a shaft 59 carrying a hand wheel 6|, thus providing for adjustment of the parts as described from a point remote to the engine 62, which in this case is shown as an aircraft motor.

In Fig. 9, I have illustrated a crank assembly corresponding in all essential respects with that previously described and illustrated in Fig. 1, with the exception that the gears I 3a and I 6a are in this case not beveled as in'the previously described embodiment, the gear M of the latter embodiment being replaced in this case by a gear I4a which operates in planes normal to the axis of the crank shaft 50. In all other respects and in the mode of operation the assembly is the same.

While the crank assembly is of primary interest in c ection with combustion engines, as herein described, it is applicable also to other mechanisms, such, for example, as pumps, and there is to be no limitation in this respect.

I claim:

1. In a crankassembly, a shaft having a crank, a connecting rod member journaled on and comprising an internal gear concentric with the crank pin, a relatively fixed internal gear concentric with the shaft axis, and a planetary gear element journaled on the crank shaft eccentrically to the axis of the shaft and of the crank pin and engaged with both of said internal gears, said planetary element occupying a plane inclined to the axes of the shaft and the crank pin and being operative to maintain a substantially fixed angular relation between said gears.

2. In a crank assembly, a casing, a shaft journaled in said casing and having a crank, a connecting rod member journaled on said crank and comprising an internal gear concentric with the crank pin, a relatively fixed internal gear of the same pitch diameter mounted on said casing concentrically with the shaft axis, and a planetary gear element journaled on the crank shaft eccentrically to the axes of the shaft and of the crank pin and engaged with said internal gears, said planetary element being operative to maintainthe first named of said internal gears in substantially 'fixed angular relation with the secondnamed internal gear.

3. In a crank assembly, a casing, a shaft journaled in said casing and having a crank, a connecting rod member journaled on saidcrank and comprising an internal gear concentric with the crank pin, a relatively fixed internal gear of the same pitch diameter mounted on said casing concentrically with the shaft axis, a planetary gear element journaled on the crank shaft eccentrically to the axes of the shaft and of the crank pin andengaged' with said internal gears, said planetary element being operative to maintain the first named of said internal gears in substantially fixed'angular relation with the secondnamecl internal gear, and means for adjusting said second-named gear angularly about the axis of said shaft.

. JOHN S. SHARPE. 

